Field of the Invention
This invention relates to illumination and display technologies, and in particular, it relates to a wavelength conversion device, light-emitting device and projection system.
Description of Related Art
Technologies using a laser or LED light source to excite a phosphor material to generate a desired single color or multi-color light have been widely used in illumination source, projection display and other application fields. Typically, the light emitted from the laser or LED illuminates a phosphor color wheel to achieve good heat dissipation.
Due to its high light utilization efficiency, reflection type color wheels are more commonly used in the type of illumination devices described above. For example, FIG. 1 shows the structure of a conventional reflection type color wheel. As shown in FIG. 1, a phosphor layer 110 is disposed on a substrate 120. The substrate 120 includes a base plate 121. To improve the reflectivity of the substrate 120 for the output light of the phosphor layer 110, the surface of the base plate 121 in conventional reflection type color wheel is treated with a silver plating technique, to reflect light incident on the surface. Specifically, the surface of the base plate 121 (such as glass or aluminum plate) is provided with a silver plating layer 122, and then coated with a transparent material (such as aluminum oxide) coating 123 to function as a anti-oxidation protective layer for the silver. The surface of the silver plating layer 122 has a very high reflectivity, up to 99%. This is very important in the reflection type phosphor wheel applications, and can typically satisfy general requirements.
However, when the power of the excitation light increases, the light output efficiency of conventional reflection type color wheel can decrease significantly.